Venetian blind slat straightener



g- 1970 v. J. RANDMARK v 3,524,337

VENE'I'IAN BLIND SLAT STRAIGHTENER Filed April 9, 1968 INVENTOR. VICTOR J RANDMARK ATTORNEYS United States Patent 3,524,337 VENETIAN BLIND SLAT STRAIGHTENER Victor J. Randmark, Toledo, Ohio, assignor to Scan- American Industries, Inc., Rossford, Ohio, at corporation of Ohio Filed Apr. 9, 1968, Ser. No. 719,932 Int. Cl. B2111 1/02 US. Cl. 72-164 Claims ABSTRACT OF THE DISCLOSURE A combination of spaced guide rollers confining the position of Venetian blind strip stock preformed to a crowned cross-section in both the lateral and normal dimension to the plane of the stock, and a set of intermediate pairs of complementary concave and convex rollers generally conforming the crown of the stock and arranged so that at least three pairs of rollers engage the stock and can be shifted laterally of the stock path between the guide means, and so that at least an intermediate pair of rollers can be shifted normal to the plane of the stock and relative to the adjacent complementary rollers. Lateral shifting is employed to correct for twist from the stock while normal shifting is to impart a longitudinal curve in the plane of the stock as for correcting down bow and up bow.

BRIEF SUMMARY OF THE INVENTION This invention relates to straightener for strip stock preformed with a crown for use as Venetian blind slats, and more particularly, to apparatus which is adjustable to work Venetian blind stock to remove up bow, down how, right-hand twist, or left-hand twist from the stock material preparatory to utilizing it in the manufacture of Venetian blinds.

It is common practice to supply strip stock for Venetian blind slats preformed to a crowned cross-ection finished and coiled on reels. Such stock may be processed, for example, as set forth in A. B. Wilson Pats. 2,294,434 for Method and Apparatus for Forming Venetian Blind Slats and Strip Material Therefor of Sept. 1, 1942, and 2,338,678 for Method and Apparatus for Forming Venetian Blind Slats of Ian. 4, 1944. Preformed slat stock as it is taken from the reels upon which it is stored for the purpose of fabrication into blinds, frequently exhibits either a bend in the longitudinal dimension of the stock, or a twist along its longitudinal dimension. When the bend of the stock is in the direction of the crown bend, it is called down bow and when it is in the opposite direction it is called up bow. When the stock is viewed with its major face generally horizontal and with the convex crown upward, if the right-hand edge of the stock lifts above the left-hand edge, this is termed right-hand twis and the converse condition is termed left-hand twist.

It is the object of the present invention to correct the bow and twist of preformed Venetian blind slat strip stock.

A second object is to impart to Venetian blind strip stock a controlled amount of up bow where it is desired to eliminate sagging of that portion of long blind slats between the supporting ladders.

In accordance with the above objects, one feature of this invention resides in apparatus for adjusting the bow and twist of Venetian blind slat strip stock, and which lends itself to imposition in a production sequence between the point of withdrawal of the stock from a reel upon which it is supplied to the blind fabricator, and the blind fabricating equipment. The apparatus includes means for confining the lateral motion of the stock as it is introduced to and withdrawn from a set of at least "ice three pairs of rollers, each pair comprising a convex and a concave mating roller, generally conforming in their curvature to the curvature of the crown of the slat stock. It is theorized that a mild working of the stock effects the correction in bow or twist achieved. This working is controlled by the positioning of the three or more pairs of complementary rollers such that when the stock is processed with its major plane in a generally horizontal path, up bow is imparted by displacing the center pair of rollers in alignment along the path and below the adjacent pairs of rollers. This setting also corrects a down how in imperfect stock conversely where an excessive back bow is encountered, it can be corrected by setting the central pair of rollers above the adjacent pairs of rollers, and in alignment therewith along the path of the stock. Twist in the stock is overcome by laterally shifting the set of three rollers relative to the path of the stock, such that the longitudinal edge of the stock which tends to droop, is passed closer to the top of the crown on the convex roll, whereby the rising longitudinal edge is carried further toward the outer extreme of the convex roll, and, thereby, is stretched with respect to its opposite edge to overcome the tendency to twist.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one form of slat straightener according to this invention.

FIGS. 2, 3 and 4 show typical relationships, as viewed along line 2-2 of FIG. 1, of the slat strip stock to a pair of complementary rollers for processing untwisted stock, stock with a left-hand twist and stock with a right-hand twist, respectively.

DETAILED DESCRIPTION The apparatus of this invention as shown in FIG. 1 comprises an input and a delivery guide means for preformed blind slat strip stock, arranged to establish a straight line path through the apparatus to which the stock is confined laterally and normal to its major face. A base 11 which is oriented generally parallel to the preformed slat strip stock shown in phantom at 12 is provided with an upstanding bracket 13 for each of the input and delivery guides 14 and 15. Pins 16 secured in the bracket 13 provide axials upon which are journalled guide rollers 17 having side flanges 18 separated by the width of the stock being processed.

One successful application of this invention has been to aluminum slat strip stock material, having a thickness of ten thousandths of an inch and a width of one inch crowned to a radius of one and three eighths inch. In such an arrangement, the flanges 18 of the guide rollers 17 are spaced only slightly greater than an inch to laterally confine the pass of stock through the straightener apparatus of the invention.

Each of the guides has been illustrated as made up of three rollers 17 arrayed as a lead and trail roller 19 and 21, and a hold down roller 22 wherein the lead and trail rollers are tangential to the desired path of the longitudinal edges of the strip stock, and the hold down roller is tangential to the crown of the stock all without imposing distorting forces upon the stock. The trail roller of the input' guide set is spaced from the lead roller of the delivery guide set about ten and one-half inches with the center to center spacing from the input to the first working roll about three inches and the pairs of working rolls being spaced on about one and one-half inch centers along the path of the stock.

With the strip confined by the guides, working is performed by the three sets of complementary straightening rolls, each comprising a convex roller 23 having a crown generally conforming to the crown of the strip stock being processed, and in the example, having a crown with the radius of one and thIee-eighths inches, and being about two inches wide for a one inch strip stock, journalled so that its face is spaced vertically below a concave roller 24 having a similar radius of curvature and spaced therefrom of the order of thirty thousandths of an inch. Each of these sets of rollers is arranged to be moved relative to the strip stock path as defined by the guide roller flanges 18. Such motion is lateral of the direction of pass and is afforded by means of the slide bracket 25 mounted in ways 26 on the base 11 and driven by means of the lead screw 27 journalled for rotation in nut 28 secured to the base 11.

The leading and trailing pair of complementary Working rolls 31 and 32 are located on the normal-neutral axis of the strip stock path, such that when the crown of the rollers 23 is aligned with the crown of the strip stock when constrained laterally by the flanges 18 and in the plane of the stock by the supporting face of lead roller 19 and trail roller 21 of the input and delivery guides 14 and 15, no working action is performed on the stock, and, in fact, in view of the spacing of the rollers, the stock passes freely therebetween as shown in FIG. 2. This orientation will be termed the lateral-neutral position. An intermediate pair of complementary crowned rollers 33 is laterally aligned with the lead and trail pair of complementary rollers 31 and 32 and is mounted for movement as a pair normal to the major face of the strip stock along the pass between the input and delivery guides 14 and 15. The pair of working rolls 33 are mounted on pins journalling the rolls, and secured on a slide 34 having tongues 35 fitting into grooves in the upstanding legs 36 of slide 25 upon which the pins journalling the rollers of the lead and trail pairs 31 and 32 are mounted. A bracket 37 extending from the upstanding portions 36 bridges the region in which the slide 34 is carried, and contains a tapped aperture through which a lead screw 38 passes. Screw 38 by its rotation adjusts the position of the slide 34 and thus the location of the pair of rollers 33 normal to the strip stock path between roller pairs 31 and 32, such that the stock can either be passed between the rollers in a straight pass, or can be caused to take a sinuous path along that pass. When roller pair 33 is aligned between pairs 31 and 32 in its elevation from base 12 it is in its normal-neutral orientation.

Twist is removed from stock withdrawn from the reel and admitted through the input guide 14 by the lateral displacement of the slide 25, such that the three sets of complementary working rolls are displaced laterally from their neutral position. The relationship of the preformed strip stock 12 to each of the pairs of complementary Working rolls when the rolls are set on their neutral positions, both laterally and in the case of the center set 33 normal to the strip is shown in FIG. 2. With both the lateral and normal settings at neutral, no working of the strip stock occurs, and it issues from the delivery guide 15 in the condition it is received at the input guide 14. Twisted stock when viewed along the lines 2-2 of FIG. 1, by definition, has a left-hand twist it the lateral edge on the left of the stock tends to rise above the lateral edge on the right of the stock. A twist of this nature can be removed on the apparatus by setting slide 25 to the right of its lateral-neutral position to relate it to the laterally constrained stock as viewed along the lines 22 as shown in FIG. 3. This results in engaging the face of the stock adjacent the longitudinal edge to the left on its upper face by the downwardly extending convex roller, while the longitudinal edge of the stock on the right is engaged on its lower face by a portion of the convex roller near the crown, thereby tending to counteract the twist existent in the unconstrained material continuously over all lengths of material carried therethrough. Similarly, a right-hand twist represented by the right longitudinal edge tending to rise above the left longitudinal edge in the unconstrained stock is corrected by displacing the working rolls to the left of their lateralneutral as shown in FIG. 4 whereby the upper roll tends to force the right-hand longitudinal edge below the position to which the left-hand longitudinal edge is carried by the crown of the convex Work rolls 23.

Down bow of the material can be corrected either separately or simultaneously with twist correction in this apparatus by displacing the center pair of working rolls 33 below their normal-neutral, thereby-tending to work the plane of the stock downward between working roll pairs 31 and 32. In order to work the stock effectively, the center to center spacing of the adjacent pairs of rollers is about the maximum diameter of the convex rollers. This enables substantial curvature of stock at the extreme settings of olfset of the center pair of rollers 33. Up bow can be removed by displacing the set of rollers 33 above the normal-neutral, thereby working in a continuous compensating down bow.

In practice, the settings of the straightener are empirically determined by running sample lengths of material through the apparatus. With skill, an operator can rapidly establish the correct settings and can so set the apparatus that twist is removed and the desired how be it zero or a slight up how can be established in a single pass through the apparatus.

While a particular form of input and delivery guide has been disclosed and exemplary dimensions set forth for a given form of strip stock, it is to be understood that the guide structure can be modified to other forms which afford appropriate prepositioning of the path of material When unconstrained by the Working rolls. Thus, for example, the delivery guide might be but a single flanged roller particularly where pinch rolls are provided closely adjacent the delivery guide in the slat cutting mechanism with which this apparatus is utilized. In addition, while three sets of complementary working rolls are utilized, more than three sets can be incorporated in the apparatus without departing from the mechanisms utilized here. It has been found that the specific structure described can be employed with a variety of thickness and widths of slat stock, and that the degree of crown of the stock need not conform exactly to the crown of the preformed strip stock.

In view of the possible variations and the modifications which can be utilized within the above teachings, it is to be understood that the preceding disclosure is intended to be illustrative of the invention, and is not to be read in a limiting sense.

Having described the invention, I claim:

1. Apparatus for straightening preformed, Venetian blind slat, strip stock having a crowned cross-section comprising an input guide laterally constraining the stock; a delivery guide laterally constraining the stock and aligned with said input guide to define a straight path for the stock; a convex working roller of greater width than the stock, and having a crown generally conforming to the stock crown; a concave working roller generally conforming to said convex roller; means mounting said concave and convex working rollers as a pair for rotation about axes which extend laterally of and are parallel to the general plane of said path, and define a plane normal to said general plane of said path, said rollers being mounted with their conforming surfaces in registry and spaced an amount of the order of and greater than the thickness of the strip stock; and means to move said set of working rollers laterally of said path.

2. Apparatus according to claim 1 including a plurality of pairs of said working rollers, each pair being positioned along said path with their axes of rotation extending laterally of and parallel to the general plane of said path and in a plane normal to said path, and means to move each of said pairs laterally of said path.

3. A combination in accordance with claim 2 including means to move said pairs of rollers in unison laterally of said path.

4. Apparatus according to claim 2 including at least three pairs of working rollers mounted with center to center spacings between pairs of the order of the maximum convex roller diameter and means to move-said pair of working rollers located between cooperating pairs of working rollers in a direction normal to the general plane of said path.

5. A combination according to claim 1 wherein said guides are flanged rollers having flanges spaced slightly greater than the spacing of the longitudinal edges of the stock and said guides are spaced from said Working rollers along said path a distance of the same order of magnitude as the width of said stock.

References Cited UNITED STATES PATENTS Haga 72-164 Wilson; 72-164 Wilson 72-161 Oftedal et al. 72-161 Stanius 72-160 X Herr 72-164 US. Cl. X.R. 

